Systems and methods for surgical navigation with a tracker instrument

ABSTRACT

There is provided a surgical instrument for navigated surgeries and systems and methods using such a surgical instrument. The surgical tool comprises a tip; a tool interface, separate from the tip; and an optically trackable target. The tip is configured to probe positions in a space and identify the positions using optical information from the optically trackable target. The tool interface is configured to mate with a surgical tool such that the optical trackable target then provides optical information with which to determine positional information for the surgical tool in the space. In one example, the system provides navigational information during surgery using the surgical instrument, namely, a single integrated tracker instrument with two or more mechanical interfaces for coupling the tracker instrument with anatomical features and/or surgical tools.

FIELD

The present application relates to surgery systems and more particularlyto systems and methods for surgical navigation with a trackerinstrument.

BACKGROUND

Navigated surgical procedures may rely on identifying anatomicallandmarks using the tip of a probe (e.g., for anatomical registration).Navigated surgical procedures may rely on measuring the relative pose ofa surgical tool (such as an acetabular cup insertion tool or a cuttingguide slot) and a patient's anatomy, and providing navigationalinformation based on the relative pose for display to an operatingsurgeon, or to a robotic control system for controlling a surgicalrobot.

There are several modalities for surgical navigation systems, includingoptical (monocular), optical (stereoscopic), inertial andelectromagnetic. FIG. 1 (Prior Art) illustrates an exemplary surgicalnavigation system 100 comprising a reference element 102 (a camera)mounted to a pelvis 104 via bone fixation hardware 106, and aninstrument 108 (aka a “tracker” or “tracker instrument”) comprising anoptically trackable target 110 (a constellation of reflective spheres).This instrument may have probe tip 112 such as for pointing tolandmarks. A computing unit, not shown, is communicatively coupled tothe camera (e.g. via cable 116 or by other manners (e.g. wirelessly) andreceives optical information (e.g. signals representing an image) fromthe camera of the optically trackable target. The computing unitprocesses the optical information, for example, using image processingoperations, computational optimizations and spatial transformations, toprovide real-time pose measurements of the instrument such as viadisplay to a display unit (not shown). The computing unit furtherdetermines navigational information based on the pose measurements, andprovides the navigational information for display or to a roboticcontrol system. Alternatively, the computing unit may save navigationalinformation in memory, and access this navigational information later inthe procedure, for example, to generate further navigationalinformation. The computing unit may execute a software workflow thatcorresponds to the surgical workflow. For example, the software workflowmay comprise a series of steps.

The navigational information is spatial information that is directly orindirectly clinically relevant. For example, the navigationalinformation may be: the position and/or orientation of an implantrelative to a patient's anatomy; spatial characteristics of a patient'spre- and/or post-surgical anatomy; the position and/or orientation of asurgical tool relative to a patient's anatomy (e.g. the location of theprobe tip). In many surgical procedure methods, different navigationalinformation is important during different steps (i.e. the same surgicalprocedure may have at least two steps, in which different navigationalinformation is important at that step). For example, in one step of atotal hip arthroplasty, an acetabular cup is inserted. During this step,the orientation of the acetabular cup relative to patient planes isimportant navigational information. In another step, a femoralprosthesis is selected and implanted; during this step, the change inthe patient's leg length is important navigational information.

Surgical procedures benefiting from different navigational informationduring different surgical steps may require a dedicated tracker for eachstep, or may require reconfiguration of a tracker for each step (e.g.attachment/reattachment of a tracker to different surgical tools). Ineither case, the cost and/or complexity of such systems is high.

SUMMARY

There is provided a surgical instrument for navigated surgeries andsystems and methods using such a surgical instrument. The surgical toolcomprises a tip; a tool interface, separate from the tip; and anoptically trackable target. The tip is configured to probe positions ina space and identify the positions using optical information from theoptically trackable target. The tool interface is configured to matewith a surgical tool such that the optical trackable target thenprovides optical information with which to determine positionalinformation for the surgical tool in the space. In one example, thesystem provides navigational information during surgery using thesurgical instrument, namely, a single integrated tracker instrument withtwo or more mechanical interfaces for coupling the tracker instrumentwith anatomical features and/or surgical tools.

In one aspect, there is a surgical instrument comprising: a tip; a toolinterface, separate from the tip; and an optically trackable target;wherein the tip is configured to probe positions in a space and theoptically trackable target is configured to provide optical informationwith which to determine the positions; and wherein the tool interface isconfigured to mate with a surgical tool such that the optical trackabletarget then provides optical information with which to determinepositional information for the surgical tool in the space.

The tip and the tool interface may be located at opposite ends of theinstrument. The optically trackable target may be located between theopposite ends.

The tool interface may be one of: a V-channel mounting interface; akinematic mount; a planar feature without a magnet; and a planar featurewith a magnet.

In one aspect there is provided a system to provide navigationalinformation during a surgery comprising: an instrument comprising: atip; a tool interface, separate from the tip; and an optically trackabletarget; a computing unit configured to: receive from a camera opticalinformation of the optically trackable target; calculate a pose of theinstrument based on the optical information; determine a position of thetip based on the pose of the instrument; determine first navigationalinformation based on the position of the tip; determine a pose of thetool interface based on the pose of the instrument; determine secondnavigational information based on the pose of the tool interface; andprovide at least one of the first and second navigational information toone or more of: a display unit for displaying to a user, computer memoryfor storage, and a robotic control system.

The instrument may have two opposite ends, and the tip is on one end,the tool interface is on the other end, and the optically trackabletarget is between the two ends.

The computing unit may be further configured to determine navigationcontext information; and provide the at least one of the first andsecond navigational information based on the navigation contextinformation. By way of example, the computing unit may determine thenavigation context information based, at least in part, on the pose ofthe instrument. By way of example, the computing unit may be configuredto execute a software workflow comprising a series of steps, anddetermine the navigation context information, at least in part, based ona current step in the software workflow.

The tool interface may be one of: a V-channel mounting interface; akinematic mount; a planar feature without a magnet; and a planar featurewith a magnet. The planar feature, whether with or without a magnet, maybe configured to mate with a cutting slot of a cutting guide.

The computing unit may be further configured to determine the positionof the tip and/or the pose of the tool interface based at least in parton calibration data. By way of example, the calibration data may bestored in memory accessible to the computing unit, and derived frommanufacturing specifications of the instrument. By way of example, thecalibration data may be determined based on a calibration routine.

The first navigational information may be a limb position change and thesecond navigational information may be an implant alignment. The surgerymay be a hip arthroplasty.

The instrument may be pre-sterilized, single-use and disposable.

The first navigational information may define at least one anatomicalaxis of a bone and the second navigational information may be thealignment of a bone cutting guide relative to the at least oneanatomical axis. The surgery may be a knee arthroplasty.

In one aspect there is provided a system to provide leg position changeinformation and acetabular implant alignment information during a hiparthroplasty surgery on a patient comprising: an instrument comprising atip, a tool interface separate from the tip, and an optically trackabletarget; wherein the tool interface is a V-channel to mate with an axisof an acetabular implant inserter tool; and a computing unit configuredto: receive optical information from a camera of the optically trackabletarget; calculate pose information of the instrument based on theoptical information; calculate a first position of the tip when incontact with a landmark on a patient's femur, prior to arthroplasty;calculate a second position of the tip when in contact with the landmarkon the patient's femur after arthroplasty; determine change in legposition information based on at least the first position and secondposition; calculate a pose of the tool interface when mated with anacetabular implant inserter tool during acetabular implant alignment;determine acetabular implant alignment information based on at least thepose of the tool interface; and provide leg position change informationand acetabular implant alignment information to a display unit.

In one aspect there is provide a system for providing navigationalinformation during a surgery comprising: pre-sterilized, single-use anddisposable components including an instrument comprising a tip, a toolinterface separate from the tip and an optically trackable target; and atracking system comprising: a camera to generate optical information ofoptically trackable targets; and a computing unit configured to executea computer-implemented workflow corresponding to a surgical workflow andprovide navigational information to a display unit based on poseinformation derived from optical information received from the camera,the camera being communicatively coupled to the computing unit; andwherein the system for providing navigational information is free fromany components requiring reprocessing for sterility. The pre-sterilized,single-use and disposable components may further include a drapeconfigured to provide a sterile barrier around the camera, the drapefurther comprising an optical window to enable the camera to generatethe optical information from within the sterile barrier.

In one aspect there is provided A computer implemented method to performa navigated surgical procedure comprising: receiving, by a computingunit from a camera, first optical information of an optically trackabletarget, the optically trackable target comprising a component of aninstrument, the instrument further comprising, separately, a toolinterface and a tip, and wherein the first optical information isreceived when the tip is in contact with an anatomical landmark;calculating, by the computing unit, a first pose of the instrument basedon the first optical information; determining, by the computing unit, aposition of the tip based on the first pose of the instrument;determining, by the computing unit, first navigational information basedon the position of the tip; receiving, by the computing unit, from thecamera, second optical information of the optically trackable targetwhen the instrument is coupled to a surgical tool via the toolinterface; calculating, by the computing unit, a second pose of theinstrument based on the second optical information; determining, by thecomputing unit, a pose of the tool interface based on the second pose ofthe instrument; determining, by the computing unit, second navigationalinformation based on the pose of the tool interface; and providing, bythe computing unit, to a display screen the first and/or secondnavigational information.

In one aspect there is provided A system to provide navigationalinformation during a surgery comprising: an instrument comprising: atip; a tool interface, separate from the tip; and an optically trackabletarget; a computing unit configured to: receive from a camera opticalinformation of the optically trackable target; calculate a pose of theinstrument based on the optical information; determine navigationcontext information based on the pose of the instrument; and responsiveto the navigation context information, perform one of: A) determine aposition of the tip based on the pose of the instrument; determine firstnavigational information based on the position of the tip; and providethe first navigational information to one or more of: a display unit fordisplaying to a user, computer memory for storage, and a robotic controlsystem; and B) determine a pose of the tool interface based on the poseof the instrument; determine second navigational information based onthe pose of the tool interface; and provide second navigationalinformation to one or more of: a display unit for displaying to a user,computer memory for storage, and a robotic control system.

These and other aspects including related computer implemented methodand/or computer readable media aspects will be apparent to those ofordinary skill in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an annotated CAD illustration of components of a surgicalnavigational system according to the prior art.

FIG. 2 is an annotated CAD illustration of a tracker instrument inaccordance with an example having a V-Channel mount as one mechanicalinterface.

FIG. 3 is an annotated CAD illustration of components of a surgicalnavigation system including a tracker instrument in accordance with FIG.2.

FIG. 4 is an annotated CAD illustration of the surgical navigationsystem of FIG. 3 with the tracker instrument coupled to an acetabularinserter.

FIG. 5 is an annotated CAD illustration of a tracker instrument inaccordance with an example having a planar feature as one mechanicalinterface.

FIG. 6 is an annotated CAD illustration of the tracker instrument ofFIG. 5 coupled to a femur to point to an anatomical landmark thereon,for example, to perform a femur registration.

FIG. 7 is an annotated CAD illustration showing the planar feature ofthe tracker instrument of FIG. 5 in an alignment with the femur forexample for a femur cut.

FIG. 8 is an annotated CAD illustration of a tracker instrument inaccordance with an example having a kinematic mount as one mechanicalinterface.

FIG. 9 is an annotated CAD illustration of details of the kinematicmount of FIG. 8.

FIG. 10 is an annotated CAD illustration of a tracker instrument inaccordance with an example having a planar feature, cylindrical inshape, as one mechanical interface.

FIG. 11 is an illustration showing an enlarged perspective view from anend of the tracker instrument of FIG. 9 showing the planar feature.

FIG. 12 is a flowchart showing a method to perform a navigated surgicalprocedure according to an example.

FIG. 13 is a flowchart showing a computer implemented method to performa navigated surgical procedure according to an example.

DETAILED DESCRIPTION

A system for providing navigational information during surgery mayprovide a single integrated tracker instrument with two or moremechanical interfaces for coupling the tracker instrument withanatomical features and/or surgical tools. For example, as shown in FIG.2, a tracker instrument 200 has one mechanical interface that is a probetip 112 similar to FIG. 1 at a first end 202 used for contacting pointsin space, such as anatomical landmarks, and another mechanical interfacethat is a tool interface. In the present example the tool interface is aV-channel 204 (e.g. a V-channel mounting interface) at a second end 206for coupling to the main shaft of a surgical tool (not shown), such asan acetabular cup inserter used in hip arthroplasty. The trackerinstrument provides an optically trackable target 110 similar to FIG. 1in the form of a pattern of reflective spheres. The tracker instrumentis a rigid body, meaning that under expected forces during use, storageor processing, the tracker instrument does not deflect mechanically.That is, it does not deflect sufficiently that the trackable targetremains accurate for tracking relative to the two or more interfaces.

The tracker instrument 200 as shown in FIG. 2 may have mechanicalinterfaces at opposite ends with the interfaces pointing approximately180° (plus or minus 25°) away from each other. For example, the probetip 112 may be at a first end 202 of the tracker instrument 200, and aV-channel tool interface 204 may be at a second end 206 of the trackerinstrument 200. The optically trackable target may be located betweenboth ends. The advantage of having mechanical interfaces at oppositeends of the tracker instrument is that there is a lower likelihood thatthe other interface will interfere with the interface being used forcoupling.

FIG. 3 is an illustration of components of a surgical navigation system220 including a tracker instrument 200 in accordance with FIG. 2. Acomputing unit (not shown) may determine the pose (in up to 6 degrees offreedom) of the two or more mechanical interfaces by receiving trackingsignals of the tracker instrument, calculating pose information of thetracker instrument based on the tracking signals, and determining thepose of the two or more mechanical interfaces based on the poseinformation. The computing unit may access calibration data defining thepositional relationship between the trackable element of the trackerinstrument and the respective mechanical interfaces to determine themechanical interfaces' respective pose(s). These poses may be computedsimultaneously or successively.

In the context of an optical localization system, the computing unit maydetermine the pose (in up to 6 degrees of freedom) of the two or moremechanical interfaces by receiving optical information of the opticallytrackable target of the tracker instrument from a camera, calculatingpose information of the tracker instrument based on the opticalinformation, and determine the pose of the two or more mechanicalinterfaces based on the pose information. The computing unit may accesscalibration data defining the positional relationship between theoptically trackable target and the mechanical interfaces to determinethe mechanical interfaces' respective pose(s).

Calibration data defines the positional relationship between thetrackable element (e.g. the optically trackable target of an opticallocalization system, or an electromagnetic probe of an electromagneticlocalization system) and the mechanical interfaces. The calibration datamay be pre-loaded onto memory of the computing unit based on themanufacturing specifications of the tracker instrument (i.e. eachtracker instrument is consistently manufactured). Alternatively, acalibration routine may be required before use, in which calibrationpose data is received by a computing unit, and calibration computationsare performed. For example, to determine calibration data of the tip ofa probe, the tracker instrument may be pivoted about the tip, while thecomputing unit receives tracking signals, determines calibration posedata representing various poses during the pivoting, and computescalibration data by executing a center-of-rotation calculation based oncalibration pose data.

The same tracker instrument may be used for spatial measurements of twoor more features (e.g. an anatomical landmark and a surgical tool). Thecomputing unit may determine navigation context information thatrepresents usage of the tracker instrument at a given point during thesurgery. The navigation context information identifies which mechanicalinterface is relevant at that moment. For example, with reference to thetracker instrument of FIG. 2 when probing anatomical landmarks, it isthe probe tip that is relevant, while the tool interface (e.g.V-channel) is not relevant. The navigation context information indicateswhich mechanical interface is relevant at a given moment. The navigationcontext information may be determined in part by the pose of the trackerinstrument. If the tracker instrument is oriented with the probe tippointing downwards (and consequently the V-channel pointing upwards),the computing unit may implement a heuristic to determine that the probetip is the currently active mechanical interface (the heuristic beingbased on the fact that it is unfeasible to have the V-channel pointingupwards during use).

If the computing unit is executing a software workflow, the navigationcontext information may be determined by the computing unit based onwhat step is being executed within the workflow. For example, when thecurrent step of the software workflow corresponds to a surgical stepinvolving the alignment of a surgical tool, the navigation contextinformation would identify the V-channel (as opposed to the probe tip)as the relevant mechanical interface.

The computing unit may use the navigation context information todetermine what to do with the navigational information. For example,certain navigational information may be stored in memory of thecomputing unit, while other navigational information may be provided toa display unit for display to a user. The navigation context informationdefines the behaviour of the computing unit with regard to how thenavigational information is provided.

The surgical localization system 220 comprising a tracker instrument 200may be used by a surgeon performing total hip arthroplasty in accordancewith the following exemplary method:

-   -   A reference element of the localization system is attached to        the patient's pelvis, the reference element being rigidly        coupled to the pelvis, the localization system being configured        to measure relative pose between the tracker instrument and the        reference element (e.g. the reference element may be a camera        attached to the pelvis as shown in FIG. 3).    -   The patient's pelvis may be registered to the localization        system by performing an anatomical registration method including        contacting multiple prescribed anatomical landmarks on the        pelvis using the probe tip of the tracker instrument. A        computing unit of the localization system determines the        position of the tip of the tracker instrument when in contact        with each respective landmark, and performs registration        computations to determine the registration between the reference        element and the patient's pelvis.    -   The hip joint is exposed.    -   Prior to dislocation of the femoral head, the baseline (i.e.        prior to arthroplasty) position of a landmark on the femur is        determined by the computing unit when the surgeon contacts the        landmark with the probe tip of the tracker instrument.    -   After dislocation and acetabular preparation, the acetabular cup        is coupled to an acetabular cup inserter for insertion into the        prepared acetabulum.    -   The surgeon couples the tracker instrument to the acetabular        inserter 400 (as illustrated in FIG. 4) so that the V-channel is        axially aligned with the axis of the acetabular inserter. When        coupled, the computing unit of the localization system        determines the orientation of the acetabular cup and provides        this information to a display unit; the surgeon views the        display unit and uses the information to adjust, select and/or        fine tune the orientation of the acetabular cup prior to        impacting it in place.    -   The surgeon prepares the femur and reduces the prosthetic joint.    -   The post-reduction (i.e. after arthroplasty) position of the        landmark on the femur is determined by the computing unit when        the surgeon contacts the landmark with the probe tip of the        tracker instrument. The computing unit further determines change        in leg position based on the spatial difference between        pre-dislocation and post-reduction femur landmark positions.

In general, the surgeon (or any other user) may invoke the computingunit to receive tracking data (e.g. from reference element 102) when theprobe (or any mechanical interface) is coupled to its respective object(e.g. anatomical landmark, surgical tool), via button presses, voicecommands, foot pedals, etc. Reference element 102 may comprise one ormore buttons 402.

The mechanical interfaces of the tracker instrument depend on the typeof surgery, including the type of existing surgical tools to which thetracker instrument must interface to facilitate clinically relevantnavigational information. A V-channel is well suited for measuringorientation of an axis. In total knee arthroplasty, navigationalinformation about the alignment of planes is important, and kneeinstrumentation provides planar cutting slots that guide planar bonecuts by an oscillating saw. A tracker instrument 500, as shown in FIG.5, provides two mechanical interfaces: a probe tip 112 and, separately,a planar feature 502 comprising the tool interface. The planar featurecomprises at least one planar surface and in the present example, twoopposing planar surfaces, for example, to interface with a cut slot of aknee cutting jig (not shown) used for TKA. The tool interface mayinclude a magnet (not shown) configured to engage the planar featurewith a portion of a tool. For example, when the planar feature isengaged with the (ferrous) cut slot, a magnetic force keeps the tool andslot engaged without the need for a user to hold them together.Furthermore, as the planar feature may not be sized for a perfect fitwithin the slot, the magnetic force may ensure that a plane of theplanar feature is fully seated on the desired surface of the cut slot.

A surgical localization system such as system 220 comprising such atracker instrument 500 may be used by a surgeon performing total kneearthroplasty in accordance with the following exemplary method:

-   -   A reference element of the localization system is attached to        the patient's femur, the reference element being rigidly coupled        to the femur, the localization system being configured to        measure relative pose between the tracker instrument and the        reference element (e.g. the reference element may be another        tracker rigidly fixed to the femur).    -   The knee joint is exposed.    -   The patient's femur may be registered to the localization system        by performing an anatomical registration method defining at        least one anatomical axis including contacting multiple        prescribed anatomical landmarks on the femur 600 using the probe        tip 112 of the tracker instrument 500 (as illustrated in FIG. 6,        where the probe tip is shown contacting the femoral epicondyle        602) and/or articulating the hip joint about its hip center of        rotation 604 while the reference element is tracked by the        localization system. A computing unit of the localization system        performs registration computations based on probe tip and/or        center of rotation data to determine the registration between        the reference element and the patient's femur. The femur        registration may be navigational information that is saved in        computer memory.    -   The patient's tibia may be registered to the localization system        by performing an anatomical registration method defining at        least one anatomical axis including contacting multiple        prescribed anatomical landmarks on the femur using the probe tip        of the tracker instrument. A computing unit of the localization        system performs registration computations based on probe tip        data to determine the registration between the reference element        and the patient's tibia. The tibia registration may be        navigational information that is saved in computer memory.    -   The planar feature of the tracker instrument is coupled with the        cutting slot of a femoral cutting jig. FIG. 7 is a CAD        illustration showing the planar feature in an alignment with the        femur (note: the cutting jig is not shown for clarity).    -   The cutting jig is fixed into alignment with the femur based on        navigational information provided on a display comprising the        orientation of the cutting plane relative to the femur as        defined by the femur registration, the navigational information        based on the calculated pose of the planar feature.    -   The femur is cut, and the cutting jig is removed.    -   The planar feature of the tracker instrument is coupled with the        cutting slot of a tibial cutting jig.    -   The cutting jig is fixed into alignment with the tibia based on        navigational information provided on a display comprising the        orientation of the cutting plane relative to the tibia as        defined by the tibia registration, the navigational information        based on the calculated pose of the planar feature.    -   The tibia is cut, and the cutting jig is removed.    -   The tibia and femur are fitted with implants, and the joint is        reduced.

FIG. 8 is an annotated CAD illustration of a tracker instrument 800, inwhich one mechanical interface is a kinematic mount 802 that isrepeatable in 6 degrees of freedom (i.e. when coupled to a matingkinematic mount, the position and orientation of the tracker instrumentis fully constrained). The other mechanical interface is the tip of aprobe 112. FIG. 9 is an annotated CAD illustration showing details ofexemplary kinematic mount 802, in which three partly spherical features902 and three magnet locations 904 are shown (note: magnets not shown).A mating kinematic mount has three slots and three magnets correspondingto the kinematic mount shown, such that the magnets impart a holdingforce keeping both sides of the mount engaged with the three partlyspherical features contacting the three slots.

FIG. 10 is an annotated CAD illustration of a tracker instrument 1000,in which one mechanical interface is a planar feature 1002, having aplanar surface 1004 cylindrical in shape, which is oriented transverseto the longitudinal axis of the tracker instrument. FIG. 11 shows apartial enlarged perspective view of tracker instrument 1000 from theend having the planar feature 1002, similar to the orientation of FIG. 9showing the details of the kinematic mount 802. Planar feature 1002 mayalso be or include a magnetic base so that the instrument may bemagnetically attached to an instrument, etc. The magnetic base may bethe entire aspect of the planar feature or there may be a magnetpositioned in a center thereof.

Determining calibration data for a tracker instrument 200 having a probetip is described earlier herein where one method describes receivingpreviously stored calibration data and a second method describesgenerating such data by pivoting the instrument about the probe tipduring a calibration routine. In a similar manner, calibration data maybe received for a tracker instrument having a planar feature. There maybe an analogous calibration routine by which to determine calibrationdata of the planar feature. For example, a user may “paint” a flatsurface with the planar feature.

The complexity of a system for performing a navigated surgical procedurecomprising a tracker instrument as described herein may be greatlyreduced. For example, the number of components required to performsurgical navigation may be reduced to: one tracker instrument; onetracking system (comprising a computing unit in communication with atracking sensor such as a camera); and one reference element.Additionally, system components may have a simplified use, since thesystem may require fewer steps for assembly and interfacing (e.g. noneed for dedicated adaptors).

In particular, the usage of the components within the sterile field maybe simplified (i.e. the reference element and the tracker instrument).In one implementation, the tracker instrument is pre-sterilized andsingle-use (disposable). Tracker instruments may be packaged in multiplelayers of protective packaging to ensure sterility, shelf life andphysical integrity. A new tracker instrument may be used for eachsurgical procedure, and the tracker instrument not require anypre-operative assembly, such as attachment of reflective spheres onto areusable tracker.

Hospital reprocessing/sterilization (e.g. autoclaving) is costly andintroduces logistical complexities when multiple surgical procedures areoccurring in a single day, since there is limited time to reprocesstools/instruments/equipment. Additionally, when new equipment is broughtinto the hospital, it must be brought in before surgery, to allow forample time for reprocessing, which typically occurs overnight.Eliminating the need for hospital reprocessing is desirable. In oneimplementation, the navigation system described herein does not requirethe reprocessing of any components:

-   -   the tracker instrument is pre-sterilized, single-use and        disposable,    -   the reference element is either pre-sterilized, single-use and        disposable or is reusable and enclosed within a sterile barrier        that is itself a pre-sterilized, single-use and disposable (such        as a camera drape providing a clear window for transmission of        optical signals, where the reference element is a reusable        camera),    -   the reference element fixation components (e.g. bone screws,        camera clamp) are pre-sterilized single-use and disposable.

The elimination of the need for hospital reprocessing is enabled by thereduction in number and simplification of system components within thesterile field. Without the reduction in number of sterile components,disposal would be prohibitively costly and raise significantenvironmental concerns. Many hospitals have strict disposal and wastepolicies, such that only a small quantity of waste may be tolerated perprocedure. Therefore, a requirement for a navigation system based onpre-sterilized, single-use and disposable components (instead ofhospital-based reprocessing) is low waste generation.

FIG. 12 is a flowchart illustrating a method 1200 to perform a navigatedsurgical procedure. At step 1202, the method comprises contacting atleast one anatomical landmark with a tip of an instrument comprising anoptically trackable target, a tool interface and the tip. At step 1204,a computing unit is invoked to execute instructions to: receive from acamera first optical information of the optically trackable target whenthe tip is in contact with the anatomical landmark; calculate a firstpose of the instrument based on the first optical information; determinea position of the tip based on the first pose of the instrument; anddetermine first navigational information based on the position of thetip. At step 1206, the method 1200 comprises coupling the instrumentwith a surgical tool via the tool interface.

At step 1208, the method 1200 comprises invoking the computing unit toexecute instructions to: with the instrument coupled to the surgicaltool, receive second optical information from the camera of theoptically trackable target; calculate a second pose of the instrumentbased on the second optical information; determine a pose of the toolinterface based on the second pose of the instrument; and determinesecond navigational information based on the pose of the tool interface.The method 1200 comprises, at step 1210, receiving by viewing a displayscreen the first and/or second navigational information. The firstand/or second navigational information may be provided to the displayscreen by the computing unit based on navigation context information.The computing unit may determine the navigation context information, forexample, at least in part based on a pose of the tool interface and/or apose of the tip.

The method 1200 may further comprise a step (not shown) of adjusting orconfirming spatial attributes related to the surgical procedure based onthe received navigational information.

FIG. 13 is a flowchart showing a computer implemented method 1300 toperform a navigated surgical procedure. The method 1300 comprises, atstep 1302: receiving, by a computing unit from a camera, first opticalinformation of the optically trackable target, the optically trackabletarget comprising a component of an instrument, the instrument furthercomprising, separately, a tool interface and a tip, and wherein thefirst optical information are received when the tip is in contact withan anatomical landmark. At step 1304, the method 1300 comprisescalculating by the computing unit a first pose of the instrument basedon the first optical information and, at step 1306, determining by thecomputing unit a position of the tip based on the pose of theinstrument. At step 1308, the method 1300 comprises determining firstnavigational information based on the position of the tip. At step 1310,the method comprises receiving, by the computing unit from the camera,second optical information of the optically trackable target when theinstrument is coupled to a surgical tool via the tool interface, and, atstep 1312, calculating by the computing unit a second pose of theinstrument based on the second optical information. There is determined,by the computing unit, a pose of the tool interface based on the secondpose of the instrument at step 1314; and, at step 1316, secondnavigational information based on the pose of the tool interface. Atstep 1318 the method 1300 comprises providing by the computing unit to adisplay screen the first and/or second navigational information.

In method 1300, the first and/or second navigational information may beprovided to the display screen by the computing unit based on navigationcontext information. It will be understood that first navigationalinformation may be determined and provided before any secondnavigational information is determined and/or provided and vice versa.The reference to “first” and “second” is disambiguate the navigationinformation and not a reference to an order of operations. The referenceto receiving optical information from the camera should not be limitedto only receiving a single instance of such information. For example,first optical information may be received at one instance in time andused to determine the first navigational information based on theposition of the tip at that instance in time. Some optical informationmay be received at a second instance of time and used to determine thesecond navigational information. Again, the first and second instancesdo not require an order of occurrence in real time.

The computing unit described herein may comprise a laptop, workstationor other computer having one or more processors (e.g. microprocessors),storage devices (e.g. RAM, ROM or other memory device, removabledevices), communication devices, buses, input devices, output devicesand/or I/O devices such as keyboard, buttons, foot pedal, pointingdevice, microphone, speaker, lights, bell, display screen (which may betouch or gesture enabled), etc. and these may be on-board or coupledthereto via communication interfaces and/or buses. Communicationinterfaces and communication devices may couple the computing unit in awired or wireless manner to one or more networks or to input, outputand/or I/O devices. Software (e.g. instructions stored in memory) mayprovide components for configuring the computing unit when the softwareis executed by the one or more processors. The various clinicalapplications and tracking modalities referred to in this description aremeant to be exemplary and non-limiting.

What is claimed is:
 1. A system to provide navigational informationduring a surgery comprising: an instrument comprising: a tip; a toolinterface, separate from the tip, the tool interface for coupling to aseparate surgical tool; and an optically trackable target; a computingunit comprising a processor and a storage device storing instructionswhich when executed by the processor configure the computing unit to:receive from a camera optical information of the optically trackabletarget; calculate a pose of the instrument based on the opticalinformation; determine a position of the tip based on the pose of theinstrument; determine first navigational information based on theposition of the tip; determine a pose of the tool interface based on thepose of the instrument; determine second navigational information basedon the pose of the tool interface; and provide at least one of the firstand second navigational information to one or more of: a display unitfor displaying to a user, computer memory for storage, and a roboticcontrol system.
 2. The system of claim 1 wherein the instrument has twoopposite ends, and the tip is on one end, the tool interface is on theother end, and the optically trackable target is between the two ends.3. The system of claim 1 wherein the computing unit is furtherconfigured to determine navigation context information; and provide theat least one of the first and second navigational information based onthe navigation context information.
 4. The system of claim 3 wherein thecomputing unit determines the navigation context information based, atleast in part, on the pose of the instrument.
 5. The system of claim 3wherein the computing unit is configured to execute a software workflowcomprising a series of steps, and determine the navigation contextinformation, at least in part, based on a current step in the softwareworkflow.
 6. The system of claim 1, wherein the tool interface comprisesa planar feature.
 7. The system of claim 6 wherein the planar featurecomprises a magnet, and is configured to mate with a cutting slot of acutting guide.
 8. The system of claim 1 wherein the computing unit isfurther configured to determine at least one of the position of the tipand the pose of the tool interface based at least in part on calibrationdata.
 9. The system of claim 8 wherein the calibration data is stored inmemory accessible to the computing unit, and derived from manufacturingspecifications of the instrument.
 10. The system of claim 8 wherein thecalibration data is determined based on a calibration routine.
 11. Thesystem of claim 1 wherein the first navigational information is limbposition change and the second navigational information is implantalignment.
 12. The system of claim 11 wherein the surgery is a hiparthroplasty and wherein the computing unit is configured to execute asoftware workflow comprising a series of steps to provide assistance forperforming the surgery.
 13. The system of claim 1 wherein the instrumentis pre-sterilized, single-use and disposable.
 14. The system of claim 1wherein the first navigational information defines at least oneanatomical axis of a bone and the second navigational information is thealignment of a bone cutting guide relative to the at least oneanatomical axis.
 15. The system of claim 14 wherein the surgery is aknee arthroplasty and wherein the computing unit is configured toexecute a software workflow comprising a series of steps to provideassistance for performing the surgery.
 16. The system of claim 6,wherein the planar feature is without a magnet, and the planar featureis configured to mate with a cutting slot of a cutting guide.
 17. Thesystem of claim 1, wherein the second navigational information relatesto the surgical tool when the surgical tool is coupled to the toolinterface.
 18. The system of claim 4, wherein the computing devicedetermines an orientation of the instrument to identify whether the tipor the tool interface is relevant in the context of the surgery todetermine which of the first navigational information and secondnavigational information is determined.
 19. A computer implementedmethod to perform a navigated surgical procedure comprising: receiving,by a computing unit from a camera, the computing unit comprising aprocessor, first optical information of an optically trackable target,the optically trackable target comprising a component of an instrument,the instrument further comprising, separately, a tool interface and atip, the tool interface for coupling to a separate surgical tool, andwherein the first optical information is received when the tip is incontact with an anatomical landmark; calculating, by the processor, afirst pose of the instrument based on the first optical information;determining, by the processor, a position of the tip based on the firstpose of the instrument; determining, by the processor, firstnavigational information based on the position of the tip; receiving, bythe processor, from the camera, second optical information of theoptically trackable target when the instrument is coupled to a surgicaltool via the tool interface; calculating, by the processor, a secondpose of the instrument based on the second optical information;determining, by the processor, a pose of the tool interface based on thesecond pose of the instrument; determining, by the processor, secondnavigational information based on the pose of the tool interface; andproviding, by the processor, to a display screen the first and/or secondnavigational information.
 20. The method of claim 19 wherein the firstand/or second navigational information is provided to the display screenby the computing unit based on navigation context information.
 21. Themethod of claim 19 wherein the tip and the tool interface are atopposite ends of the instrument.